Two geological phenomena in one precarious locale: a towering stone window, and a deep blue void.

The fishing boats that moor in this small lagoon enter and leave through a tunnel to the sea.

This unique building in the main square stands out among the city's typically Baroque architecture.

This Stone Age solar temple aligns with the sun on each equinox and solstice.

This subterranean necropolis holds three floors of antler-dug grave caves.

A minotaur, a labyrinth, and a dubious restoration pull in visitors from around the world.

While not Turkey's deepest underground city, this subterranean redoubt is the largest.

In this historic region, homes and churches are carved into ancient volcanic rock formations.

This arch granting triumphal entrance into Antalya was designed to honor the emperor's visit.

A marvel of Byzantine engineering under the streets of Istanbul.

An ancient octagonal weather station named for the eight Greek gods of wind.

This ancient Greek place of assembly and marketplace is being revealed layer by layer below the modern Athens cityscape.

The hallucinogenic center of the ancient world.

Monasteries on rock pillars, once accessible only by frayed ropes.

An abandoned Byzantine fortress and notorious prison.

A curious cave church carved into the face of a cliff.

Its frescoes depict the likeness of Marshal Tito, Karl Marx, and Friedrich Engels burning in hell.

This exclusive resort has completely covered a tiny Balkan island in a 5-star warren of guest rooms.

A beautiful mountaintop mausoleum devoted to a Montenegrin icon can't seem to make everyone happy.

A tiny church on a man-made island in the Adriatic.

A wunderkammer of gold and silver reliquaries and ancient saintly bones.

The big toe of this towering monument to a Croatian national hero is worn from years of superstitious rubbing.

When a supermarket opened up shop within a medieval building it became protected by UNESCO on a technicality.

A whimsical bridge adorned with decorative dragons.